[unreadable] Radiation sources are used throughout our society. By law, each radiation source must be properly shielded. Presently, design of shielded facilities or assemblies is performed via extensive and laborious hand calculations and with simple analytical tools that make use of broad simplifying assumptions. This application proposes the development of a simple, easy-to-use software package for shielded facility design and effective dose determination. Such a package will allow the user to evaluate a range of different shielding scenarios in which materials and/or layout are iteratively altered. This capability is prohibitively laborious and tedious with existing hand calculation approaches. The proposed software package will launch by icon from the users computer desktop using a pre-installed JAVA application. All details regarding radiation sources, facility and detector/phantom locations will be supplied by the user via an easy-to-use design interface. The software will then interpret all entries and assemble an appropriate input file to be run with the MCNP Monte Carlo code. Use of the MCNP code as the simulation engine allows full 3D modeling of the realistic scenario, including many radiation types, creation of secondary particles and full accounting for all interaction processes, something not possible with existing approaches. In addition, users will be able to calculate effective dose equivalent, also not possible with the hand calculation approach which provides estimates of exposure or air kerma. All simulations will be performed on multiple tiered secure servers, freeing the user's computer for other tasks and limiting unauthorized access to the MCNP code. Technical challenges include creating a fully interactive 3D user interface, development of strategies allowing nearly unlimited flexibility in facility and source design, automating formation of a complex MCNP input file based on simple user inputs, creating a secure network application, and maintaining server integrity. [unreadable] [unreadable] [unreadable]